We have quite many RSS feeds for lots of different things on Lets Make Robots. Here's a list:
These contain all content within a category - we also have more specific feeds listed below.
The front page — the frontpage, now as RSS.
Robot projects — robot projects only.
Tips/walkthroughs — tip/walkthroughs only.
Forum topics — forum topics from all forums.
Blogs — posts from all blogs
Letsmakerobots has a blog for every user, and also an RSS feed for each blog. I won't list them all here, but the address for them is something like this http://letsmakerobots.com/blog/4/feed where "4" is the user number. You can an also find it just by visiting the blog you want. If you have a browser that supports RSS feeds, you should see the orange RSS icon light up somewhere, probably near the address bar.
Categories, tags, forums, etc.
In our system, categories, tags and forums is basically the same thing, and fortunately, these all have their own RSS feeds. So, whenever you visit a forum page or click on a tag, you should see that RSS icon described above light up.
If that's not the case or you just want to dig around manually, all these RSS feeds follow the pattern of http://letsmakerobots.com/taxonomy/term/97/0/feed where 97 is the forum/category/tag-number.
All comments — all comments, sidewide.
There are also alternate feeds for comments on specific robot projects, tips/walkthroughs, blog/forum posts etc. - you should see the RSS icon light up when you visit one of these also. If you want to find them manually, their addresses are like http://letsmakerobots.com/crss/node/41 where 41 is the "node" number for that specific post.